An optical Illusion consisting of a spinnable top marked in black with the pattern shown above. When the wheel is spun (especially slowly), the black broken lines appear as green, blue, and red colored bands!
References
Cohen, J. and Gordon, D. A. ``The Prevost-Fechner-Benham Subjective Colors.'' Psycholog. Bull. 46, 97-136, 1949.
Festinger, L.; Allyn, M. R.; and White, C. W. ``The Perception of Color with Achromatic Stimulation.'' Vision Res. 11,
591-612, 1971.
Fineman, M. The Nature of Visual Illusion. New York: Dover, pp. 148-151, 1996.
Trolland, T. L. ``The Enigma of Color Vision.'' Amer. J. Physiology 2, 23-48, 1921.